Brightness adjustment can be desirable for images and videos that were gathered with non-ideal exposures. However, saturation can be adversely affected when the images and videos are lightened or darkened. Insufficient saturation can occur when dark colors are lightened and when light colors are darkened. In images with insufficient saturation, colors appear less lively and less vibrant. Over-saturation can occur when dark colors are darkened and when light colors are lightened. In oversaturated images, details become more difficult to discern.
It would be desirable to adjust the brightness without adversely affecting saturation.
It would also be desirable to increase the brightness directly in a luminance-chrominance space. Certain image rendering devices have digital imaging pipelines that work directly in luminance-chrominance space. Consider a luminance-chrominance digital television that has a pipeline for processing MPEG images, and printer having a pipeline for processing JPEG images. MPEG and JPEG images are based on luminance-chrominance color space. For these devices, adjusting brightness directly in luminance-chrominance space can be advantageous, because unnecessary color conversions are avoided. For example, a printer that adjusts brightness directly in luminance-chrominance space can avoid an extra conversion to another color space for lightness adjustment (e.g., RGB); and a luminance-chrominance digital television that adjusts brightness directly in luminance-chrominance space can avoid an extra conversion to another color space for lightness adjustment (e.g., RGB).